How do I order ids based on some logical ranking, let's say I have IDs of 1,2,3,4,5. But I want to rank them in order of 3,4,2,1,5. Here Id 3 is most important category and should be ranked first. Ids are Int

probably your own class Id extending comparator is a good idea here

I don't get the logic for the ordering, do you just want 3 to be first? Or you have a whole arbitrary order for every possible ID, and you want to order lists of IDs according to this "master list"?

Yeah, the general answer is 'use a custom comparator', but this is an underspecified question (or maybe an XY problem)

@Joffrey Yes, Master list would be right way to think of it. Not just 3, that was just an example. Master list is list of Ints. Ids are ints.

In this case I would probably build a map from this "master list", from each ID to its position in the order, and use that to write a custom sort function like this:

/** Defines the total order between all IDs */
private val order = listOf(3, 4, 2, 1, 5)

/** Maps each ID to its rank in the total order */
private val rankById = order.withIndex().associate { (index, id) -> id to index }

private fun List<Int>.sortedByCustomOrder() = sortedBy { rankById[it] }

fun main() {
    println(listOf(1, 2, 3, 4, 5).sortedByCustomOrder()) // [3, 4, 2, 1, 5]
    println(listOf(1, 2, 3).sortedByCustomOrder()) // [3, 2, 1]
    println(listOf(2, 4, 5).sortedByCustomOrder()) // [4, 2, 5]
}

Thanks. How can I pass this to sortedWith(compareBy ( { sorting logic 1 }, { sorting logic 2 }, { /*HERE - ranking logic*/ }) )